o 

 <r 

 o 



28 



24 



20 



16 



12 



8 



4 

 x 



° 



12,000 



11,000 



■J 10,000 



d 9,000 



z 



z 8,000 



o 



* 7,000 



o 5,000 



4,000 

 3,000 

 2,000 

 1,000 



CHLOROPHYLL o 



ZOOPLANKTON 



JUL. 'AUG. 'SEP. ' OCT ' NOV. ' DEC. 'JAN. ' FEB. 'MAR. ' APR. 1 MAY 'jUN. 'JUL. ' AUG ' SEP ' OCT ' NOV 'DEC. 

 1967 1968 



Figure 10. Average chlorophyll a (a) and zooplankton (b)in the lower Columbia River, 1967-68. 



Water Temperature 



The highest average temperatures in 1967 

 and 1968 were 22.7° C. in late August 1967 and 

 21.3° C. in mid-August 1968 (fig. 6). The 

 lowest average temperature was 5.1° C. in 

 January 1968. 



Turbidity 



Turbidity is directly correlated with river 

 flow. Griffin, Watkins, and Swenson (1956) 

 attributed the late February rise in turbidity 

 to the increased flow of tributaries into the 

 lower Columbia River during the winter rainy 

 season and the increase in mid-June to the 

 increased flow from tributaries into the upper 

 Columbia when the spring snow melted. The 

 higher turbidity at stations 2 and 5 than at 

 neighboring stations (fig. 1 1 ) in this study was 

 attributed to inflow of the Willamette and 

 Cowlitz Rivers, respectively. 



I 2 3 4 5 6 



STATION 



Finure 11. — Average turbidity at each sampling station, 

 July 1967 through December 1968. 



